How to Disable Ctrl-Alt-Delete in Ubuntu

Having a physical access to the keyboard can simply use the Ctrl+Alt+Delete key combination to reboot the server without having to logged on, But we can prevent the use of this key combination on a production server for an accidental reboots.

To disable the reboot action taken by pressing the Ctrl+Alt+Delete key combination,

Comment out the following line in the file /etc/init/control-alt-delete.conf
#exec shutdown -r now "Control-Alt-Delete pressed"

$sudo vim /etc/init/control-alt-delete.conf